This system features the 4-piston, S4 caliper mounted to a 11", 2 piece slot, drill, zinc plated rotor. The S4 caliper has D.O.T compliant dust and weather seals and uses the popular DR1 or HB100 pad type. Billet aluminum hubs come assembled with premium bearings packed with Redline synthetic grease and billet dust caps. Rotors are pre-assembled with NAS high grade stainless hardware. All mounting brackets and hardware are also included. The 11" SS4+ is designed just like Baer's larger systems, but in a smaller package for 15" wheels.